1. Field of the Invention
The present invention relates to a semiconductor device that communicates wirelessly.
2. Description of the Related Art
In recent years, an individual identification technique which employs wireless communication with an electromagnetic field, radio waves, or the like has attracted attention. In particular, an individual identification technique which employs an RFID (radio frequency identification) tag as a semiconductor device which communicates data via wireless communication has attracted attention. An RFID tag (hereinafter simply referred as an RFID) is also referred to as an IC (integrated circuit) tag, an IC chip, an RF tag, a wireless tag, and an electronic tag. An individual identification technique which employs an RFID is beginning to be made use of in production, management, and the like of individual objects, and it is expected that this technique will also be applied to individual authentication.
The RFIDs can be divided into two types: an active type RFID tag having a built-in power supply that is necessary for the circuit operation accompanied with reception and transmission data between the tag and a reader/writer, and a passive type RFID tag driven with generating electric power in the tag using electric power of radio waves or electromagnetic waves (carrier waves) from the outside (regarding the active type, see Reference 1: Japanese Published Patent Application No. 2005-316724, and regarding the passive type, see Reference 2: Japanese Translation of PCT International Application No. 2006-503376). The active type RFID has a built-in power supply for driving the RFID, and includes a battery as the power supply. Meanwhile, in the passive type RFID, electric power for driving the RFID is made by using electric power of radio waves or electromagnetic waves (carrier waves) from the outside. Therefore, the passive type RFID has a structure which does not include a battery.